Joint input shaping and feedforward for point-to-point motion: Automated tuning for an industrial nanopositioning system

Feedforward control can effectively compensate for the servo error induced by the reference signal if it is tuned appropriately. This paper aims to introduce a new joint input shaping and feedforward parametrization in iterative feedforward control. Such a parametrization has the potential to significantly improve the performance for systems executing a point-to-point reference trajectory. The proposed approach enables an efficient optimization procedure with global convergence. A simulation example and an experimental validation on an industrial motion system confirm (i) the performance improvement obtained by means of the joint input shaping and feedforward parametrization compared to pre-existing results, and (ii) the efficiency of the proposed optimization procedure.     

Signal-error-feedforward-controlled amplifiers

Signal-error feedforward can be used to control the performance of amplifier systems. Feedforward, unlike feedback, does not require signal loops, and therefore results in inherently stable systems. Some practical feedforward-amplifier configurations are given, followed by a numerical example that demonstrates the improvement obtained from the application of signal-error feedforward.     

改进的多用户波束赋形算法

为了减少多用户MIMO系统中用户间的相互干扰,增加系统的吞吐量,提出一种基于用户发送信号最小泄露准则(SLNR)的多用户线性波束赋形算法--CB-SLNR算法,该算法通过确定收发双方码本矩阵,基站选择合适的codebook对发送信号赋形,同时通过控制信息传递其他用户码本索引信息,使接收端易于采用MMSE检测算法恢复发送信号.仿真表明CB-SLNR算法很好地改善了系统吞吐量.     

Adaptive nulling loop control for 1.7-GHz feedforward linearizationsystems

An adaptive analog control system is introduced for the nulling loop (first loop) of a 1.7-GHz feedforward linearization system. The sensitivity to temperature and frequency variations is experimentally shown for a conventional feedforward system, leading to the need for an adaptive control system. Two error signals based on detected power levels are introduced and used to control the nulling loop vector modulator to ensure cancellation of the main signal. Finally, the experimental performance of this system is presented     

Feedforward signal prediction for accurate motion systems using digital filters

A positioning system that needs to accurately track a reference can benefit greatly from using feedforward. When using a force actuator, the feedforward needs to generate a force proportional to the reference acceleration, which can be measured by means of an accelerometer or can be created by double differentiation of the reference position.The positioning system’s response to the feedforward usually shows some delay, caused by calculation time of the digital control computer, the digital-to-analog converter that drives the actuator’s amplifier, and digital differentiation of the reference position. At higher frequencies, even a small delay causes a large tracking error. Prediction of the feedforward signal by one or two samples can reduce this error.This paper describes three methods to predict a feedforward signal over a time span of a few samples. Polynomial extrapolation of past data does not require knowledge of the signal’s properties. Sinusoidal extrapolation produces an exact prediction at a set of chosen design frequencies. Both filter types can be implemented as FIR filters. A particular form of frequency sampling filters, having digital zeros which are not each other’s conjugates, can also be used for prediction purposes. The complex filter output allows reconstruction of input signal properties and its prediction. The filters are compared with regard to their suitability for predicting feedforward signals.     

Amplifier systems with quasifeed-forward control

The applicability of signal-error feedforward is usually restricted, owing to the output signal adder that is required. A quasifeedforward configuration is presented here which extends the improvement obtained by feedforward to this output adder. A practical example is given with the numerical results that were obtained.     

数字自适应前馈功放线性化研究

本文研究了一种新的前馈线性化功放的结构,省去了导频信号,在经典的两环前馈法基础上引入第三环,通过第三环直接提取交调信号,同时在线性化功放系统中引入了DSP控制器,用最优化算法进行控制,实现了对线性化功放的自适应控制。此方案被用于cdma2000基站功放的设计,使三载波CDMA信号输出的ACPR低于-51dB。     

Random vibration test control of inverter-fed electrodynamic shaker

The random vibration control of an inverter-fed electrodynamic shaker is presented in this paper. First, the dynamic model of the shaker is found and a current-controlled pulsewidth modulation inverter is designed and implemented. The feedback controller is augmented with a command feedforward controller and a disturbance feedforward controller to let the armature exciting current have low harmonic content and possess excellent waveform tracking performance. Then, an acceleration controller and its random vibration command are arranged. In the proposed acceleration control scheme, a command feedforward controller and a robust disturbance feedforward controller are also employed to let the shaker have close random acceleration command waveform tracking control performance, and the performance be insensitive to the system parameter variations. It follows that the acceleration control with desired frequency response in a vibration test could be achieved through properly setting the command signal. The effectiveness of the proposed control scheme is verified by simulation and measured results     

Robust speed control of IM with torque feedforward control

The authors describe a digital signal processor-based (DSP-based) robust speed control for an induction motor (IM) with the load-torque observer and the torque feedforward control. In the proposed system, the load torque is estimated by the minimal-order state observer based on the torque component of a vector-controlled IM. Using the load-torque observer, a speed controller can be provided with a torque feedforward loop, thus realizing a robust speed control system. The control system is composed of a DSP-based controller, a voltage-fed pulsewidth modulated (PWM) transistor inverter and a 3.7 kW IM system. An eccentric load with an arm and a weight is coupled to the IM and it generates the sinusoidal gravitational fluctuating torque. Experimental results show robustness against disturbance torque and system parameter change     

自适应前馈射频功率放大器设计

在高功率射频放大器设计时，通常采用前馈技术来改善宽带信号的线性度。本文基于普通的前馈系统。提出了一种新的自适应前馈线性化技术，并结合信号包络检测技术进行带外信号调节。同时，还利用该技术在计算机仿真系统上设计了一个射频功率放大器的功放输出级，通过对仿真结果的比较，发现他能显著改善IMD性能。     

Nonlinear control of an electrohydraulic injection molding machinevia iterative adaptive learning

Examines the control of an industrial injection molding machine (IMM) for both mold filling and mold packing. The machine is a Boy 50 Ton system operated by hydraulics with electronically controlled valves. A nonlinear model of the system is determined for the filling and packing stages, then verified against experimental data. The model includes several key aspects of the actual machine dynamics including stick-slip friction, time delays, nonlinear valve flow characteristics, and deadzones. A feedforward control input is determined via an iterative learning control scheme. This input is combined with either a feedback strategy or an open-loop strategy for the filling and packing control phases, respectively. The time delay, which exists in both stages, is accounted for by time shifting the learning feedforward signal relative to the feedback control signal. Simulation and experimental investigations indicate the benefits of the proposed strategy for control of electrohydraulic IMMs. Subsequent to demonstrating the benefits for fill-stage and pack-stage learning control, a complete cycle, including fill-to-pack transfer, is demonstrated     

Robust tracking servo system considering force disturbance for the optical disk recording system

This paper proposes a new robust tracking servo system for the optical disk recording system with feedforward controller based on the prediction of the tracking error. In optical recording systems, the feedback servo system must suppress the influence of force disturbance and parameter variation. To overcome this problem, this paper designs the robust feedback control system by using coprime factorization and disturbance observer. The detecting signal of the optical disk recording system is only a tracking error. Hence, the feedforward controller of the proposed tracking control system is constructed based on both the "zero-phase-error tracking" control theory and the prediction of the tracking error. The experimental results point out that the proposed tracking servo system has a quick and precise tracking response and keeps the residual tracking error below its tolerance.     

基于前馈电流控制斜坡补偿的Boost功率因数校正零交越失真研究

该文提出了一种前馈电流控制的斜坡补偿方法,将该方法引入到临界导通Boost 功率因数校正(PFC)转换器的设计中,以减小零交越失真问题,改善谐波电流和频率对系统的限制。基于临界导通Boost PFC转换器的拓扑结构,理论分析了前馈电流控制斜坡补偿技术对脉冲宽度调制(PWM)信号占空比的调制作用,推导出补偿斜率与输入线电压的关系式,迫使线电压零交越点附近的电流跟随电压变化。仿真和测试结果表明,该方法可有效抑制零交越失真现象,提高系统的动态性能,尤其在高频及轻负载情况下。测得Boost PFC转换器的总谐波失真(THD)仅为3.8%,功率因数0.988,负载调整率3%,线性调整率小于1%,效率达到97.3%。有效芯片面积为1.611.52 mm2。     

Linearization and feedforward compensation for switching systems

The linearization of a switching system including a feedforward compensation for power supply perturbations is obtained by the addition of a high-frequency signal. A general expression for the required shape and amplitude of this high-frequency signal is derived. The method is analyzed for its application to AC phase control systems. The method is outlined for the case of a DC electric motor phase control. It is then generalized to any nonlinear switching system     

Active noise control: a tutorial review

Active noise control (ANC) is achieved by introducing a cancelling “antinoise” wave through an appropriate array of secondary sources. These secondary sources are interconnected through an electronic system using a specific signal processing algorithm for the particular cancellation scheme. ANC has application to a wide variety of problems in manufacturing, industrial operations, and consumer products. The emphasis of this paper is on the practical aspects of ANC systems in terms of adaptive signal processing and digital signal processing (DSP) implementation for real-world applications. In this paper, the basic adaptive algorithm for ANC is developed and analyzed based on single-channel broad-band feedforward control. This algorithm is then modified for narrow-band feedforward and adaptive feedback control. In turn, these single-channel ANC algorithms are expanded to multiple-channel cases. Various online secondary-path modeling techniques and special adaptive algorithms, such as lattice, frequency-domain, subband, and recursive-least-squares, are also introduced. Applications of these techniques to actual problems are highlighted by several examples     

An Adaptive Feedforward Amplifier Under “Maximum Output” Control Method for UMTS Downlink Transmitters

An adaptive feedforward amplifier is implemented for a Universal Mobile Telecommunication System (UMTS) downlink channel (2110–2170 MHz). An exhaustive characterization of the space of solution has corroborated the feedforward theoretical behavior. As a result, an alternative adjustment method is proposed, called “maximum output,” which entails maximizing a specific designed objective function. Besides this, an adaptive control system, based on distortion signal minimization architecture, has been fabricated in order to apply the designed method. The overall system performance achieves significant improvements such as 16.7 dB on the third-order intermodulation product, measured with a 5-MHz separated two-tone signal, 15 dB on the adjacent channel leakage ratio level and 2.7 dB on the output power level, both of them obtained with UMTS test model 1 (64 channels). The maximum output control method allows fulfilling any standard linearity specification while power efficiency is maximized so the desired tradeoff between linearity and efficiency is achieved.     

基于加速度计的光电跟踪系统等效复合控制

复合控制是提高光电跟踪系统跟踪精度的一种有效方法,它较好地解决了精度和稳定性之间的矛盾;而等效复合控制是复合控制的另一种实现。为了实现等效复合控制,采用加速度计直接测得加速度信息再通过积分得到的速度作为前馈控制信号。实验对比结果表明,加速度计可以作为等效复合控制的传感器,在实际应用中实现伺服跟踪系统精度的提高,加入等效复合控制的光电跟踪伺服系统的跟踪精度提高至原来的6.67倍。     

Precise position control of shape memory alloy actuator using inverse hysteresis model and model reference adaptive control system

Position control of Shape Memory Alloy (SMA) actuators has been a challenging topic during the last years due to their nonlinearities in the governing physical equations as well as their hysteresis behaviors. Using the inverse of phenomenological hysteresis model in order to compensate the input–output hysteresis behavior of these actuators shows the effectiveness of this approach. In this paper, in order to control the tip deflection of a large deformation flexible beam actuated by an SMA actuator wire, a feedforward–feedback controller is proposed. The feedforward part of the proposed control system, maps the beam deflection into SMA temperature, is based on the inverse of the generalized Prandtl–Ishlinskii model. An adaptive model reference temperature control system is cascaded to the inverse hysteresis model in order to estimate the SMA electrical current for tracking the reference signal. In addition, a closed-loop proportional–integral controller with position feedback is added to the feedforward controller to increase the accuracy as well as eliminate the steady state error in position control process. Experimental results indicate that the proposed controller has great accuracy in tracking some square wave signals. It is also experimentally shown that the suggested controller has precise tracking performance in presence of environmental disturbances.     

基于导频检测技术的射频前馈功放研究

介绍了基于导频检测技术的前馈射频功放线性化技术,从理论上简单地分析了前馈功放以及利用导频信号自适应控制前馈功放的原理.利用导频法控制前馈有很多地电路结构,包括导频跳频、导频信号扩展和导频调制.导频法检测技术是一种简单而有效的控制技术,该技术的关键是选择合适的导频信号频率和信号的大小.通过对选定的最新的元器件,采用典型的导频前馈法用ADS进行仿真,并给出仿真结果,然后提出一个实际有效的导频法线性化方案.     

基于改进的PID稳定平台伺服控制系统

传统PID控制在伺服系统高精度位置跟踪和改善系统品质方面已露出诸多不足,且系统中存在的控制干扰和测量噪声会在很大程度上影响伺服系统的跟踪精度。针对工作实际中的被控对象控制问题,对传统的PID控制算法进行改进。提出一种带有卡尔曼滤波器的重复控制补偿PID和前馈补偿相结合的控制方法。通过仿真证明,该控制方法能以较高的精度跟踪周期性输入信号,且有较好的抑制随机扰动和鲁棒性。